one of the things they look at is the location, boston marathon the date on tax day, on patriots day, four or five days before the anniversary of waco. these are all images and symbols that investigators are sifting through to see if that had anything to do with the message that was put here with these two bombs at the boston marathon. they can't rule out overseas, foreign terrorism and they looking at all of that trying to determine who was behind this and why. >> shep: you might have thought in the moments after this bombing that when these pressure cookers exploded they would have exploded in a lot of pieces. what these pictures seem to indicate, very large pieces held together. we see numbers identifying marks. we see materials that are clearly, according to your sources, the materials that held this bomb as it sat either in a trash can or side 56 curb. these are very valuable pieces of evidence which i'm getting will be iconic pieces. i'm getting there are reporters all over boston are wondering how in atlanta came across this? >> i would love to tell you, shepard, i think we'll